This invention relates generally to a control valve for a hydraulic circuit, and in particular to a control valve for keeping a constant viscosity or temperature of a pressure medium in the hydraulic circuit by means of a throttle provided on a slider of the valve and by a thermally expandable control element which controls the circulation of the presence medium in response to its temperature.
In a known control valve of this kind the thermally extendable control element acts immediately on the valve body. In addition, a partial stream of the pressure medium flowing through a throttle flows around the thermally extandable control element and consequently the sensing of the temperature and thus the temperature control is relatively inaccurate. In the event that the throttle is clogged the pressure medium becomes overheated.